Memory devices using magnetism such as a hard disk drive (HDD) and a magnetoresistive RAM (MRAM) have been developed.
As a technology applied to MRAM, “spin transfer switching” that reverses the direction of magnetization of a magnetic substance by passing a current through the magnetic substance is studied as a mode of writing data to MRAM. The spin transfer switching is a technology that reverses the direction of magnetization of a magnetic substance (magnetic layer) in a magnetoresistive effect element by passing a write current into the magnetoresistive effect element and using spin-polarized electrons generated inside the magnetoresistive effect element.
A magnetization state inside a nano-scale magnetic substance can be relatively easily controlled using a local magnetic field by the spin transfer switching, as described above. Further, the value of a current to reverse the magnetization can also thereby be made smaller in accordance with fineness of the magnetic substance.
Development of MRAM of high storage density is promoted by use of the spin transfer switching. Thus, the element size of the magnetoresistive effect element as a memory element being reduced to 30 nm or less is desired.
It is generally difficult to process materials containing magnetic metal such as Co and Fe used for the magnetoresistive effect element by dry etching (for example, RIE). Thus, such materials are frequently etched physically by irradiating the materials with an ion beam using an inert gas such as Ar.